fix: Improve content type handling in streamable_http.go #210

TBXark · 2025-04-25T15:28:00Z

Optimized content type header parsing

Changed from direct string comparison to proper media type parsing using mime.ParseMediaType()
This handles cases where the Content-Type header includes additional parameters (like charset)
More robust parsing of content types while maintaining the same functionality
Fixes potential false negatives when comparing raw Content-Type strings

Test case

package main

import (
	"fmt"
	"mime"
)


func main() {
	tests := []struct {
		name     string
		input    string
	}{
		{"Standard JSON", "application/json"},
		{"With charset", "application/json; charset=utf-8"},
		{"Mixed case", "APPLICATION/JSON"},
		{"Whitespace", "  application/json  "},
		{"Plain text", "text/plain"},
		{"Event stream", "text/event-stream"},
		{"Empty string", ""},
		{"Broken param", "application/json;=broken"},
		{"Subtype", "application/json-seq"},
		{"With boundary", "application/json; boundary=foo"},
	}
	for _, t := range tests {
		mediaType, _, err := mime.ParseMediaType(t.input)
		if err != nil {
			fmt.Println("err:", err)
			continue
		}
		fmt.Println(mediaType)
	}
	
}

application/json
application/json
application/json
application/json
text/plain
text/event-stream
err: mime: no media type
err: mime: invalid media parameter
application/json-seq
application/json

Other

I didn't handle the error here. If processing fails, it will default to the original code's default case.

Summary by CodeRabbit

Bug Fixes
- Improved handling of HTTP response Content-Type headers for more accurate recognition of supported formats.
Style
- Minor formatting improvements for cleaner code structure (no impact on functionality).

coderabbitai · 2025-04-25T15:28:06Z

Walkthrough

The update refines how the HTTP response Content-Type header is processed in the SendRequest method. Instead of directly matching the raw header string, the code now uses mime.ParseMediaType to extract and compare only the media type, ignoring any additional parameters. The logic for handling "application/json" and "text/event-stream" responses remains unchanged. Additionally, some minor whitespace cleanup was performed in the SSE event processing goroutine to improve code formatting, without affecting functionality.

Changes

File(s)	Change Summary
client/transport/streamable_http.go	Switched to parsing Content-Type with `mime.ParseMediaType` for robust media type matching; performed minor whitespace cleanup in SSE event processing goroutine.

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coderabbitai

Actionable comments posted: 1

📜 Review details

Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between b46fa54 and d35c451.

📒 Files selected for processing (1)

client/transport/streamable_http.go (4 hunks)

🔇 Additional comments (2)

client/transport/streamable_http.go (2)

10-10: Add the mime import for media type parsing
This import enables use of mime.ParseMediaType to robustly extract the media type from the Content-Type header.

252-259: Approve whitespace cleanup in SSE handler
The removal of extraneous blank lines around JSON unmarshal calls improves readability without altering behavior.

coderabbitai · 2025-04-25T15:29:57Z

client/transport/streamable_http.go

+	mediaType, _, _ := mime.ParseMediaType(resp.Header.Get("Content-Type"))
+	switch mediaType {
 	case "application/json":
 		// Single response
 		var response JSONRPCResponse


🛠️ Refactor suggestion

Ensure robust error handling when parsing Content-Type
Currently, parsing errors from mime.ParseMediaType are ignored, which may lead to an empty mediaType and fall into the default case for malformed headers. It’s safer to handle errors explicitly and fallback to the raw header (or its trimmed subtype) to preserve existing behavior.

Proposed diff:

- mediaType, _, _ := mime.ParseMediaType(resp.Header.Get("Content-Type")) + rawCT := resp.Header.Get("Content-Type") + mediaType, _, err := mime.ParseMediaType(rawCT) + if err != nil { + // Fallback to the raw content type (trimmed, lowercase) without parameters + mediaType = strings.ToLower(strings.TrimSpace(strings.SplitN(rawCT, ";", 2)[0])) + }

TBXark · 2025-04-25T15:32:17Z

I discovered this problem when using the Streamable HTTP API provided by https://mcp.higress.ai. Because it returns the content-type as application/json; charset=utf-8

fix: Improve content type handling in streamable_http.go

d35c451

coderabbitai bot reviewed Apr 25, 2025

View reviewed changes

ezynda3 merged commit 33c98f1 into mark3labs:main Apr 26, 2025
2 checks passed

adlternative pushed a commit to adlternative/mcp-go that referenced this pull request May 20, 2025

fix: Improve content type handling in streamable_http.go (mark3labs#210)

0f1eea4

coderabbitai bot mentioned this pull request Jul 9, 2025

fix Content-Type: application/json; charset=utf-8 error #478

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fix: Improve content type handling in streamable_http.go #210

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Optimized content type header parsing

Test case

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